Ortho-ethoxy-n-n-diethylbenzamide insect repellent compositions and process of applying same



United States Patent ORTHO ETHOXY -N N DIETHYLBENZAMIDE INSECT REPELLENT COMPOSITIONS AND PROCESS OF APPLYING SAME Edward T. McCabe, Hyattsville, Md.; dedicated to the gree use of the People in the territory of the United tates No Drawing. Application February 26, 1953, Serial No. 339,188

8 Claims. (Cl. 167-30) (Granted under Title 35, U. S. Code (1952), sec. 266) A non-exclusive, irrevocable, royalty-free license in the invention herein described, for all governmental purposes, throughout the world, with the power to grant sublicenses for such purposes, is hereby granted to the Government of the United States of America.

The invention herein described is hereby dedicated to the free use of the people in the territory of the United States.

This invention relates to a new insect repellent and to a method for its preparation.

It has been found that ortho-ethoxy-N,N-diethylbenzamide, a compound having the formula when applied to either the human skin or articles of clothing affords effective protection against insect bites by repelling the insects. This protection is particularly effective against Aedes aegypti. In using the new repellent compound, it may be applied either alone or in an inert carrier.

A number of tests to measure the repellency of this compound against Aedes aegypti was conducted by spreading the material on the arms of test personnel, who then thrust their arms into cages containing the mosquito. The arms were exposed at 30-minute intervals for 3 minutes each or until the first insect bite. It was found that the application of ortho-ethoxy-N,N-diethylbenzamide to the skin affords protection against Aedes aegypti for an average of 308 minutes.

Tests to measure the repellency of this compound as an impregnant for fabric against Aedes aegypti were conducted by uniformly impregnating mercerized cotton hose with the compound at a rate equivalent to 3.3 grams per sq. ft., drawing the hose over the arms of test personnel,

who then thrust their covered arms into cages containing Aedes aegypti for 1 to 2 minutes. If no bites or less than 5 bites were received the tests were repeated on each successive day until five or more bites during one exposure were received. It was found that fabric impregnated with ortho-ethoxy-N,N-diethylbenzamide remained repellent against the mosquito for at least 37 successive days.

For ease of application to the skin the ortho-ethoxy- F N,N-diethylbenzamide is incorporated in a suitable inert liquid or solid carrier. The following examples are merely illustrative of the invention and are not intended as limitations of its scope.

20 parts by weight of ortho-ethoxy-N,N-diethylbenz amide are mixed with 80 parts by weight of carrier to produce the following compositions:

(l) 20 parts amide with parts of isopropanol.

(2) 20 parts amide with 80 parts of mineral oil.

(3) 20 parts amide with 80 parts of petrolatum.

(4) 20 parts amide with 80 parts of a white emulsion of fatty acid esters mixed with wtaer. This composition is obtained by mixing 20 parts of the amide with 20 parts of the fatty acid esters, pouring the mixture into sufficient water to make a total of parts, and. then emulsifying the mixture.

(5) 20 parts of amide with 80 parts of a standard zinc oxide ointment.

The compound, ortho-ethoxy-N,N-diethylbenzamide is a new compound and was prepared as follows:

18.4 grams (0.1mole) of ortho-ethoxybenzoyl chloride dissolved in 50 milliliters of dry ether is slowly added to a cooled solution of 14.6 grams (0.2 mole) of diethylamine dissolved in 100 milliliters of dry ether. After the reaction product has been stirred for 1 hour at room temperature, enough cold water is added to dissolve the precipitated diethylamine hydrochloride. The reaction mixture separated into two layers, namely, an ether and an aqueous layer. The ether layer is separated and washed successively with 100 milliliter portions of 5% hydrochloric acid solution, water, 5% sodium hydroxide solution, water and finally with a saturated solution of sodium chloride. After the ether extract has been filtered through a cotton plug, the ether is removed at the water pump and the residue is purified by vacuum distillation. A water-white distillate is obtained, boiling point 121 C. at 0.1 mm., n =1.516O.

One nonobvious advantage of this repellent is that it does not harm or deleteriously affect plastic materials such as watch crystals, eyeglass frames or fountain pens usually found on or about the person to whom the repellent will be applied.

Having thus described my invention, I claim:

l. An insect repellent fabric comprising fabric impregnated with ortho-ethoxy-N,N-diethylbenzamide.

2. An insect repellent composition comprising orthoethoxy-N,N-diethylbenzamide in an inert insecticidal adjuvant as a carrier therefor.

3. The composition of claim 2 wherein the carrier is isopropanol.

4. The composition of claim 2 wherein the carrier is mineral oil.

5. The composition of claim 2 wherein the carrier is petrolatum.

6. The composition of claim 2 wherein the carrier is an emulsion of fatty acid esters in water.

7. The composition of claim 2 wherein the carrier is a zinc oxide ointment.

8. A process of repelling insects comprising applying ortho-ethoxy-N,N-diethylbenzamide to the region from which the insects are to be repelled.

References Cited in the file of this patent UNITED STATES PATENTS 2,408,389 Geitler Oct. 1, 1946 FOREIGN PATENTS 403,892 Great Britain Ian. 4, 1934 OTHER REFERENCES Couturier (I), Annales des Chimie, vol. 10, series 11 (1938), pp. 563 and 628.

Couturier (II), Comptes Rendus, vol. 205 (1937), pp. 800 to 802. 

2. AN INSECT REPELLENT COMPOSITION COMPRISING ORTHOETHOXY-N,N-DIETHYLBENZAMIDE IN AN INERT INSECTICIDAL ADJUVANT AS A CARRIER THEREFOR. 